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| Home > Publications database > Ab-initio Rechnungen zum Zusammenhang zwischen Magnetismus und Struktur ultradünner Filme |
| Book/Report | FZJ-2019-01867 |
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1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21838
Report No.: Juel-3364
Abstract: This work presents a study of the ground-state atomic and magnetic structure of unsupported 3d transition-metal monolayers (UML). We performed total energy calculations on the basis of the density functional theory in the local spin-density approximation (LSDA) using the full-potential linearized augmented-plane wave method (FLAPW) in film geometry as a function of the lattice parameters, crystal structure, and magnetic order. The atoms are arranged in a two-dimensional (2D) square lattice or in a (2D) hexagonal lattice and we included nonmagnetic, p(1 x 1)-ferromagnetic and c(2 x 2)-antiferromagnetic structures. Antiferromagnetism on a hexagonal lattice leads to noncollinear spin-configurations, which we approximated by a c(2 x 2)-antiferromagnetic structure on a centered rectangular lattice. The results are summarized in a structure table. The UMLs at the beginning of the 3d-series (Ti, V) are nonmagnetic and crystallize in the closed packed hexagonal structure; Fe, Co and Ni are hexagonal with a ferromagnetic ground-state spin-structure. In the middle of the 3d-series Mn and Cr are antiferromagnetic and there is a strong competition between the hexagonal and the square lattice: The ground-state found for Mn is hexagonal and for Cr quadratic. The ground-state lattice constants of 2D-magnets are found to be generally smaller than those of the bulk materials. A distinct magneto-volume effect was found, with a maximum volume expansion for hexagonal Mn (12%). The work on the structural stability of UMLs was repeated for the lattice constant of Cu. In the case of Mn and Fe in the geometry of Cu(001) we found that magnetism is responsible for a transition from the square lattice being the ground-state structure for a nonmagnetic film to a hexagonal lattice. We think that this is directly related to the surface reconstructions observed for Fe and Mn on Cu(001). This work gives also an introduction to the basic theory underlying the FLAPW method. Results for different exchange and correlation potentials are discussed. Tests of different charge-density mixing-methods are provided.
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